Applet throwing exception when running it through web browser

I have written an applet program. It has some references to classes from java tools.jar in it (eg:- import com.sun.jdi.connect.IllegalConnectorArgumentsException)

When I run this applet through appletviewer utility it works fine. But when I embed this applet in HTML file and try to run it through web browser, I am getting exception about some classes not found at runtime:-